Throughout this disclosure, various publications, patents and published patent specifications are referenced by author and/or by citation. The disclosures of all publications, patents and published patent specifications are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
Technological advancement demands new types of transducer materials that can efficiently sense and convert force and energy from one type to another for signal processing and modulation, switching and actuation, sensing and energy harvesting. Additional desirable features include the ability to mimic the hearing system where deformation of cylindrical stereocilia cells in response, to sound pressure in the cochlea of the inner ear is converted into electrical signals to excite the auditory nerve. Similarly, it can imitate the vision system where shape change due to photoisomerization of rhodopsin molecules in rod and cone shaped cells in retina upon light irradiation will induce a change of electrical current to excite the optic nerve.
New transducer materials are essential for science and technology advancement. For example, being able to convert solar energy into electrical energy provides the potential for green energy harvesting, harness vibrational energy to power sensing network and medical implants (Wang et al., “Piezoelectric nanogenerators for self-powered nanodevices”, IEEE Pervas Comput 2008, 7 (1), 49-55; Op het Veld et al., “Harvesting mechanical energy for ambient intelligent devices”, Inform. Syst. Front. 2009, 11 (1):7-18; Paradiso and Starner “Energy scavenging for mobile and wireless electronics”, IEEE Pervas Comput 2005, 4 (1):18-27) and new adaptive and autonomous materials for space mirror and unmanned aerial vehicles.
Current transducer materials in general suffer from one or more of the following shortcomings: (i) complex and bulky architectures; (ii) high power consumption and low coupling efficiency; (iii) slow response; (iv) limited bandwidth; (v) poor reliability caused by hysteresis and fatigue and (vi) sensitivity limited to one type of stimuli.
Nanocomposite materials with combined best properties of two distinct materials could provide the necessary advantages. In spite of enormous research activities, the technology and science of nanocomposites are still in their infancy. This is largely due to the lack of ability of synthesizing nanocomposites with controlled morphology and interface characteristics. The persistent challenges include poor dispersion and interfacial strength. The best reported Young modulus of CNT composites to-date is only 10% of what was predicted (Huynh et al., Science 2002, 295, 2425-2427; Law et al., Nature Materials 2005, 4, 455-459). Therefore, to capitalize unique nanomaterial properties, not only is a new processing and fabrication strategy required but also the interface needs to be reinforced for effective load and energy transfer.
ZnO nanowires have shown the ability to harvest low-frequency vibrational energy and therefore is one nanocomposite material that has been studied (Xu et al. (2010) Nature Nanotechnology 5:366-373). However, only less than 1.0% of mechanical energy was converted into electricity. This exemplifies the importance of a cohesive interface which is capable of efficiently transferring energy across the boundary to minimize loss. It also indicates that a system that contains a large number of nanostructures acting constructively is needed to produce sufficient signal strength for real-world applications.
To summarize, the field of nanocomposites is largely unexplored but offers great technological promise. Inability to control density, location and orientation of functional nanowires have hampered the advanced of nanocomposites-based science and technology. To the best of Applicants' knowledge, no materials that combine high deformable nature of polymers with other materials to create new light-weight and energy efficient actuators which can create amplified motion and miniature energy harvesting devices that can convert various ambient energies into electricity have been reported. This invention reports such a material and its multifunctional use.